Implantable medical leads having oscillating cable conductor lumens

ABSTRACT

An electrical implantable lead includes an elongated lead body having a plurality of lumens therein, including at least one linear lumen and at least one planar, non-linear lumen and a plurality of conductor cables disposed within the plurality of lumens. The electrical implantable lead further includes a terminal connector coupled to a proximal end of the lead body, the terminal connector being in electrical communication with at least one of the plurality of conductor cables. Further, the electrical implantable lead includes at least one electrode coupled to the lead body, the at least one electrode in electrical communication with at least one of the plurality of conductor cables. In accordance with various embodiments, the at least one non-linear lumen extends longitudinally along a portion of the lead body and includes a plurality or crests and a plurality of troughs.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 13/688,016,now U.S. Pat. No. 8,886,336 filed Nov. 28, 2012, which claims thebenefit of U.S. Provisional Application No. 61/564,431, filed Nov. 29,2011, which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to medical devices. More specifically, theinvention relates to an elongate implantable medical lead and methods ofmanufacturing the medical lead.

BACKGROUND

Implantable medical leads are devices that deliver electrical signals toimplantable medical devices. Exemplary implantable devices are cardiacrhythm management (CRM) systems (e.g., pacemakers, defibrillators, andcardiac resynchronization therapy devices) and neurostimulation systems(e.g., spinal cord stimulation (SCS) systems). For CRM systems, medicalleads are typically advanced intravascularly to an implant locationwithin or on a patient's heart, while for neurostimulation systems, suchleads are typically positioned beneath the skin, in vessels located inthe neck or limbs, in the pectoral region, in the epidural space of thespinal cord, or intramuscularly.

Implantable leads typically include a flexible conductor surrounded byan insulating tube or shaft that extends from an electrode at the distalend to a connector terminal at the proximal end. Many leads incorporatemultiple connectors extending from an electrical contact on a connectorterminal to an electrode on a distal end of the lead body. When theconnector terminal is coupled to an implantable device, and the deviceand lead are implanted in a patient, certain stresses or strains maydevelop in portions of the lead body or conductors near the terminalconnector, or regions of a lead that experience bending.

SUMMARY

In Example 1, the present invention is an implantable medical leadincluding an elongated lead body having a plurality of lumens therein,including at least one linear lumen and a first non-linear lumen. Aplurality of conductor cables are disposed within the plurality oflumens. The implantable medical lead further includes a terminalconnector coupled to a proximal end of the lead body, the terminalconnector in electrical communication with at least one of the pluralityof conductor cables. Further, the implantable lead includes at least oneelectrode coupled to the lead body, the at least one electrode inelectrical communication with at least one of the plurality of conductorcables. The first non-linear lumen extends longitudinally along aportion of the lead body and includes a plurality of crests and aplurality of troughs.

Example 2 is the implantable medical lead of Example 1, furthercomprising a second non-linear lumen extending longitudinally along aportion of the lead body.

Example 3 is the implantable medical lead of either Examples 1 or 2,wherein the plurality of lumens have a circular cross-section.

Example 4 is the implantable medical lead of any of the Examples 1-3,wherein the first and second non-linear lumens are offset from a centralaxis of the elongated lead body.

Example 5 is the implantable lead of any of the Examples 1-4, whereinthe series of crests and troughs define a sinusoidal pattern with adefined amplitude and a defined frequency.

Example 6 is the implantable lead of any of the Examples 1-5, whereinthe defined amplitude is between about 10 and about 50 mm and furtherwherein the defined angular frequency is between about 0.1 and about 0.7mm.

Example 7 is the implantable lead of any of the Examples 1-6, whereinthe series of crests and troughs are formed in a linear plane in atwo-dimensional manner.

Example 8 is the implantable lead of any of the Examples 1-7, whereinthe series of crests and troughs are formed in a rotational plane in athree-dimensional manner.

Example 9 is the implantable lead of any of the Examples 1-8, whereinthe first non-linear lumen and the second non-linear lumen have equalfrequencies and amplitudes.

Example 10 is the implantable lead of any of the Examples 1-9, whereinthe first non-linear lumen has a first frequency and the secondnon-linear lumen has a second frequency that is not equal to the firstfrequency.

Example 11 is the implantable lead of any of the Examples 1-10, whereinthe first non-linear lumen extends along the portion of the lead bodyextending about 10 to about 50 mm from the terminal connector.

In Example 12, the present invention is a method of manufacturing animplantable medical lead. The method includes extruding a polymericmaterial through a die configured to create a plurality of lumens withinthe implantable electrical lead. The plurality of lumens extend along alongitudinal axis of the die. The method also includes twisting the diewith respect to the longitudinal axis alternatively in a clockwise and acounterclockwise direction while extruding such that twisting in theclockwise direction creates a trough and in the counterclockwisedirection creates a crest in the plurality of the lumens. The methodfurther includes disposing a conductor cable in each of the plurality ofthe lumens.

In Example 13, the present invention is a method of manufacturing animplantable medical lead, which includes holding a cable in tension in amold and adjusting the cable using a plurality of guiding pins to createa plurality of planar crests and troughs within the cable, and injectinga molten material into the mold to form a lead body around the cable,such that the cable extends longitudinally along a portion of the leadbody.

Example 14 is the method of manufacturing an implantable medical lead ofExample 13, further including removing the cable from the mold such thata lumen with the series of crests and troughs is created.

Example 15 is the method of manufacturing an implantable medical lead ofExamples 13 or 14, wherein the cable is at least one of a conductorcable, a Nitinol wire, and a cable with a lubricious coating.

Example 16 is the method of manufacturing an implantable medical lead ofany of Examples 13-15, further including filling holes created by theplurality of guiding pins with a molten material.

Example 17 is the method of manufacturing an implantable medicalelectrical lead of any of Examples 13-16, wherein the molten material isone of Liquid Silicone Rubber (LSR) and a medical adhesive.

Example 18 is the method of manufacturing an implantable medical lead ofany of the Examples 13-17, wherein the molten material is LSR.

Example 19 is a method of manufacturing an implantable medical lead. Themethod includes providing a core pin made of a shape memory metal, thecore pin having a first generally sinusoidal configuration and a secondgenerally linear configuration, injecting silicone rubber having adurometer of between about Shore 60D and about Shore 40A over the corepin while in the first generally sinusoidal configuration to form a leadbody, cooling the core pin such that the core pin is in the secondgenerally linear configuration, removing the core pin from the lead bodyso that the lead body defines a lumen having a generally sinusoidalconfiguration, and inserting a conductor into the lumen.

Example 20 is an electrical implantable lead, wherein the implantablelead includes an elongated lead body having a plurality of lumenstherein and a plurality of conductor cables disposed within theplurality of lumens. The plurality of conductor cables including atleast one non-linear conductor cable. The electrical implantable leadfurther includes a terminal connector coupled to a proximal end of thelead body, the terminal connector being in electrical communication withat least one of the plurality of conductor cables. Further, theelectrical implantable lead includes at least one electrode coupled tothe lead body, the at least one electrode in electrical communicationwith at least one of the plurality of conductor cables. In accordancewith various examples, the at least one non-linear conductor cable isconfigured to be disposed and extend longitudinally along a portion ofthe lead body and includes a plurality of crests and a plurality oftroughs.

While multiple embodiments are disclosed, still other embodiments of thepresent invention will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the invention. Accordingly, the drawings anddetailed description are to be regarded as illustrative in nature andnot restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B are perspective views of an implantable medical device andan electrical implantable lead according to various embodiments.

FIGS. 2A-2B are perspective views of the electrical implantable lead,according to various disclosed embodiments.

FIGS. 3A-3B illustrate schematic views of a portion of the electricalimplantable lead with different orientations of the lumens according tovarious embodiments.

FIGS. 4A-4C illustrate different sinusoidal oscillations of differentamplitudes and frequencies in lumens of the electrical implantable leadaccording to various embodiments.

FIGS. 5A-5D illustrate cross-sectional views of the electricalimplantable lead that includes plurality of oscillating lumens accordingto various embodiments.

FIGS. 6A-6E illustrate a system for manufacturing the electricalimplantable lead according to a disclosed embodiment.

FIG. 7 is a flowchart depicting an exemplary method for manufacturing anelectrical implantable lead or a portion of the lead.

FIGS. 8A-8B illustrate implantable electrical lead segments havingdifferent oscillating lumen orientations according to variousembodiments. FIG. 8C illustrates a cross-sectional side view of FIG. 8Balong line A-A.

FIG. 9 is a flowchart illustrating an exemplary method for manufacturingan electrical implantable lead or a portion of the lead.

FIG. 10 is a schematic view showing various cross-sections of anelectrical implantable lead having an oscillating lumen.

FIG. 11 illustrates a perspective view of a portion of the electricalimplantable lead with lumens according to various embodiments.

FIG. 12 illustrates a perspective view of a portion of the electricalimplantable lead that includes a linear lumen and oscillating conductorcables.

FIG. 13 illustrates an exemplary method for manufacturing an electricalimplantable lead or a portion of the lead.

While the invention is amenable to various modifications and alternativeforms, specific embodiments have been shown by way of example in thedrawings and are described in detail below. The intention, however, isnot to limit the invention to the particular embodiments described. Onthe contrary, the invention is intended to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1A is a perspective view of an implantable cardiac rhythmmanagement (CRM) system 10. As shown, the system 10 includes animplantable rhythm management device 12 (e.g., a pulse generator) and animplantable electrical lead 14, which includes a lead body 22 thatextends from a proximal portion 18 to a distal portion 20. As shown inFIG. 1, the heart 16 includes a right atrium 26, a right ventricle 28, aleft atrium 30 and a left ventricle 32. As shown, the heart 16 includesan endocardium 34 covering the myocardium 36. In some embodiments, afixation helix 24, located at an end of the distal portion 20 of thelead 14, penetrates through the endocardium 34 and is embedded in themyocardium 36. In some embodiments, the fixation helix 24 iselectrically active and thus operates as a helical electrode for sensingthe electrical activity of the heart 16 and/or applying a stimulatingpulse to the right ventricle 28. In one embodiment, the CRM system 10includes a plurality of leads 14. For example, it may include a firstlead 14 adapted to convey electrical signals between the pulse generator12 and the right ventricle 28 and a second lead (not shown) adapted toconvey electrical signals between the pulse generator 12 and the rightatrium 26 or coronary veins (not shown).

FIG. 1B is a perspective view of a representative implantableneurostimulation (e.g., spinal cord stimulation) system 110. As shown inFIG. 1B, C1-C8 are the cervical vertebrae and nerves, T1-T12 are thethoracic vertebrae and nerves, L1-L5 are the lumbar vertebrae andnerves, and S1-S5 are the sacrum and coccyx and the sacral nerves. Otherimplantable neurostimulation systems include deep brain stimulation andperipheral (e.g., vagal) nerve stimulation systems. As shown in FIG. 1B,a neurostimulation system 110 according to various embodiments includesan implantable device or pulse generator (IPG) 112 that generateselectrical stimulation pulses used for stimulation. The IPG 112 iscoupled to a lead 14 having a proximal portion 18 and a distal portion20 extending to an electrode array 38 at or near an end of the distalportion 20. The electrical stimulation provided by the IPG 112 throughthe electrode array 38 may be used for numerous purposes including, forexample, masking sensed pain.

FIG. 2A is a perspective view of the lead 14, according to variousdisclosed embodiments, for use in an implantable system such as forexample a CRM system 10 or a neurostimulation system 110. As shown, aconnector assembly 40 is disposed at or near the proximal region 18 ofthe lead 14, while a distal assembly 42 is disposed at or near thedistal portion 20 of the lead 14. Depending on the functionalrequirements of the system 10 (see FIG. 1A) or system 110 (see FIG. 1B)and the therapeutic needs of a patient, the distal portion 20 mayinclude one or more electrodes. As shown, the distal portion 20 includesa pair of coil electrodes 44 and 45 that can function as shockingelectrodes for providing a defibrillation shock to the heart or as lowvoltage pace or sense electrodes. Various electrode combinations may beincorporated into the lead 14 within the scope of the variousembodiments of the present disclosure (e.g., one or more coil or ringelectrodes). As shown in FIG. 2A, the connector assembly 40 includes aconnector 46 and a terminal pin 48. The connector 46 is configured to becoupled to the lead body 22 and is configured to mechanically andelectrically couple the lead 14 to a header on the pulse generator 12(see FIG. 1A) or the IPG 112 (see FIG. 1B). As shown in FIG. 2A, thedistal assembly 42 includes a radiopaque marker 50 and a fixation helix24.

FIG. 2B illustrates a perspective view of a portion of the electricalimplantable lead 14 according to various embodiments. The electricalimplantable lead 14 may be interchangeably referred to as lead 14. Thelead 14 includes an elongated lead body having one or more lumens 52 and54 extending longitudinally along a portion or substantially the entirelength of the lead 14 in a non-linear fashion. The non-linear pathdefined by the lumens 52 and 54 may have several configurations,including for example oscillating, waveform-shaped, or W-shaped. Asshown in FIG. 2B, the lumens 52 and 54 have a series of crests andtroughs including crests 56, 58 and troughs 60, 62. According to variousembodiments, the lumens 52 and 54 extend in different planeslongitudinally along the lead 14. In other embodiments of the invention,the crests and troughs extend longitudinally along the lead 14 in thesame or substantially the same plane. Many embodiments disclosed hereinrefer to a lead 14 including lumens 52 and 54 having a non-linear oroscillating shape. Each such embodiment includes an alternativeembodiment in which the lead 14 does not includes lumens, but insteadthe lead 14 is formed directly around a conductor (e.g., a cableconductor), such that no lumen is formed.

In various embodiments, one or both of the lumens 52 and 54 extendlongitudinally along the lead 14 along a three-dimensional path,including for example a generally spiral or generally helical path.Also, in some embodiments, one or both of the crests and troughs of thelumens 52 and 54 may define a waveform shape having a variable amplitudeand/or a variable frequency. In other embodiments, the lumens 52 and 54may have a constant amplitude and frequency. Further, the lead 14 mayinclude a plurality of conductor cables 64 and 66 disposed in the lumens52 and 54 such that the lumen 52 includes a first conductor cable 64 andthe lumen 54 includes a second conductor cable 66. According to someembodiments, each of the non-linear lumens have the same (orsubstantially the same) amplitude and angular frequency. According toother embodiments, the amplitude, the angular frequency, or both aredifferent in one non-linear lumen as compared to another non-linearlumen.

The non-linear or oscillating path defined by the lumens 52 and 54provides a slack to the conductor or cable by allowing for the length ofthe conductor or cable to exceed a corresponding length of the leadbody. This slack in the conductor cables 64 and 66 may minimize strainand stress in the conductor cables 64 and 66 associated with flexuralbending of the lead 14 in vivo. The portions of the lead body that maybe optimized to provide increased amount of slack include, for example,the terminal flex region of a cardiac lead, the neck portion of vagalstimulation leads, material transition regions, or joints (e.g.,polyurethane to silicone) along a lead body. Further, in embodiments ofthe present disclosure, the electrical implantable lead 14 are made of apolymeric material. It will be apparent to a person of ordinary skill inthe art that the polymeric material for the electrical implantable lead14 may be any known biocompatible polymeric material.

FIGS. 3A and 3B illustrate schematic views of a portion of theelectrical implantable lead 14 with different orientations of the lumens52 and 54 according to various embodiments. FIG. 3A illustrates a seriesof crests (including crests 56 and 58) and troughs (including troughs 60and 62) in the lumens 52 and 54 that have equal (or substantially equal)amplitudes and magnitudes. FIG. 3B illustrates a series of crests(including crests 56 and 58) and troughs (including troughs 60 and 62)in the lumens 52 and 54 that have equal (or substantially equal)amplitudes but opposite magnitudes.

FIGS. 4A-4C illustrate various exemplary embodiments where theoscillations in lumens 52 and 54 may extend as sinusoidal oscillationshaving a plurality of crests and troughs with defined amplitudes (A) andangular frequencies (ω). As shown, each of the amplitude and frequency(or both) may be adjusted to vary the path of the lumens 52, 54, whichin turn varies the amount of slack in the cables extending through thelumens. As shown for example in FIG. 4A, the lumens of the implantablelead 14 extend as sinusoidal oscillations having crests 56, 58 andtroughs 60, 62 defining an amplitude of A and a frequency of ω. As shownfor example in FIG. 4B, the lumens of the implantable lead 14 extend assinusoidal oscillations having crests 56, 58 and troughs 60, 62 definingan amplitude of 2 A and a frequency of ω. As shown for example in FIG.4C, the lumens of the implantable lead 14 extend as sinusoidaloscillations having crests 56, 58 and troughs 60, 62 defining anamplitude of A and a frequency of 2ω.

The amplitudes and frequencies may be selected and optimized toconfigure the desired sinusoidal oscillations in the lumens 52 and 54such that the oscillations provide a desired about of slack in theconductor cables to minimize or prevent strain in the conductor cablesduring bending motion. In exemplary embodiments of the presentdisclosure, the amplitudes (A) and frequencies (ω) of the lumens 52 and54 may be optimized throughout the length of the lead 14. In otherembodiments of the present disclosure, the amplitudes and frequencies ofthe lumens 52 and 54 may be optimized in desired portions of the lead14. In some embodiments of the present disclosure, for example, inportions of the lead 14 that are prone to substantial bending, thelumens 52 and 54 are configured to have an increased amplitude orfrequency (or both) to allow for further slack in the conductor cable.Further, various parameters of the lead 14 may be taken intoconsideration in selecting the optimized amplitude and frequencyincluding, for example, materials of the lead 14, materials of theconductor cables, length of the lead 14, diameter of the lead 14,diameter of the conductor cables, bending angles of the conductorcables, and axial tension in the conductor cables. According toexemplary embodiments, a portion of the lead near the terminal connectorincludes oscillating lumens.

According to some embodiments, a portion of the lead body extending fromabout 10 mm to about 50 mm from the terminal connector includesoscillating lumens. According to other embodiments, a portion of thelead body extending from about 10 mm to about 25 mm from the terminalconnector includes oscillating lumens. According to other embodiments, aportion of the lead body extending about 20.32 mm from the terminalconnector includes oscillating lumens. In the various disclosedembodiments, the lumens may have a variety of amplitudes and angularfrequencies. According to various exemplary embodiments, the oscillatinglumens have amplitudes of about 1 mm and an angular frequency of about0.309 mm, which results in a lumen length of about 20.8 mm. In theseembodiments, the lumen thus allow for an excess length of about 0.48 mm(i.e., 20.8 mm minus 20.32 mm), which allows for strain relief for aconductor placed within the lumen. It will be apparent to a person ofordinary skill in the art that various other parameters may be takeninto consideration without deviating from the scope of the invention.According to various embodiments, the oscillating lumens have amplitudesof between about 0.1 and about 2.0 mm. According to various embodimentsthe oscillating lumens have an angular frequency of between about 0.1and about 0.7 mm.

FIGS. 5A-5D illustrate cross-sectional views of an electricalimplantable lead 14 including a plurality of oscillating lumens 52, 54according to various embodiments. As shown in FIG. 5A, the lead 14includes two oscillating lumens 52, 54 that are radially offset fromcenter axis of the lead 14. FIG. 5B shows a lead 14 having threeoscillating lumens radially offset from the center axis of the lead 14.FIG. 5C shows the lead body 14 with four oscillating lumens thatradially offset from the central axis of the lead 14 and generallyequally spaced about a circumference of the lead body. FIG. 5D shows thelead body 14 with plurality of oscillating lumens that are radiallyoffset from the central axis of the lead 14 and generally equally spacedabout a circumference of the lead body.

FIGS. 6A-6E illustrate exemplary methods 210 and 220 for manufacturingthe electrical implantable lead 14 using injection molding techniques.In these embodiments, lumens may or may not be formed within the lead14. In other words, the conductors may be molded directly into the lead14 or a temporary structure (e.g., a Nitinol wire) may be used duringthe molding process and then removed to expose a lumen which may then belater loaded with a conductor. Thus, while the following descriptionrefers to directly forming the conductor within the lead 14, thedisclosed methods may also be used to form lumens into which a conductormay be later inserted.

FIGS. 6A-6C illustrate a method 210 for manufacturing the implantablelead 14. As shown in FIG. 6A, a plurality of holding pins 68 hold orsupport a plurality of conductor cables 64 in tension in a mold. FIG. 6Bshows a plurality of guiding pins 70 disposed between the plurality ofthe conductor cables 64. FIG. 6C shows translation of the guiding pins70 to impart a non-linear (e.g., W-shaped, undulating, or oscillating)configuration to the conductor cables 64. This non-linear configurationmay include a series of crests 56, 58 and troughs 60, 62 of desiredamplitude and frequency. In some embodiments, the desired amplitude andfrequency may be achieved by increasing or decreasing the number ofguiding pins or changing the lateral offset (e.g., spacing from alongitudinal centerline of the lead) between successive guiding pins 70.Once the conductor cables 64 are held in the desired configuration bythe holding pins 68 and the guiding pins 70, the lead body is formed bystandard injection molding techniques as are known in the art. After thelead body is formed by injection molding, the holding pins 68 andguiding pins 70 may be removed. The resulting spaces or lumens may befilled with a suitable material (e.g., silicone rubber or medicaladhesive), to complete the formation of the lead body. The method shownwith reference to FIGS. 6A-6C will create a lead 14 having aconfiguration as shown in FIG. 8.

FIGS. 6D-6E illustrate a method 220 for manufacturing an implantablelead 14. As shown in FIG. 6D, a major lumen core pin 69 includes holes72 a, 72 b to support the guiding pins 70 located in dynamic sections 74a, 74 b. As shown in FIG. 6E, the guiding pins 70 are inserted into theholes 72 a, 72 b and are then used to rotate the dynamic sections 74 inopposite directions. The dynamic sections 74 may be rotated with theguiding pins 70 about a longitudinal axis of the core pin 69 asufficient amount to achieve the desired amplitude and frequency. Thistechnique may be used to impart a non-linear configuration, which may beeither planar or three dimensional.

FIG. 7 is a flowchart showing an exemplary method 700 for manufacturingan electrical implantable lead 14 (or a segment of the lead 14). Themethod 700 begins with holding a cable (or conductor such as, forexample Nitinol) in tension in a mold (step 710). According to variousembodiments, the cable may be made fromnickel-cobalt-chromium-molybdenum alloys (e.g., MP35N), silver alloys,tantalum alloys, or any other material commonly used in conductors foran implantable medical lead. In various embodiments, the cable includesan insulating coating, which may include a lubricious coating. Next, thecable is adjusted using a plurality of guiding pins to create aplurality of planar crests and troughs within the cable (step 720).After creating the crests and troughs within the cable, a moltenmaterial may be injected into the mold (step 730). In variousembodiments, the molten material may be Liquid Silicone Rubber (LSR).The molten material is cured to set the series of crests and troughswithin the cable. The method 700 may further include removing the cablefrom the mold such that a lumen with the series of crests and troughs iscreated. The method 700 may further include filling holes created by theplurality of guiding pins with LSR or a medical adhesive.

Exemplary lead segments resulting from the process of method 700 areshown in FIGS. 8A-8C. As shown in FIG. 8A, the lead segment 801 includesthree conductor lumens 76 having the same (or substantially the same)angular frequency (ω), with one conductor lumen 76 having a firstamplitude and two conductor lumens having a second, greater amplitude.According to various embodiments, the configuration of the lead segment801 includes one lumen 76 having an amplitude of A and two lumens 76having and amplitude of 2 A, such as shown for example in FIGS. 4A and4B. As shown in FIG. 8B, the lead segment 802 includes three conductorlumens 76 having the same (or substantially the same) angular frequency(ω), with two of the conductor lumens 76 having a first amplitude and athird conductor lumen 76 having a generally opposite amplitude. FIG. 8Cshows a cross-sectional side view along line A-A of FIG. 8B showing thelead segment 802 and the path of conductor lumen 76 in a plane.

FIG. 9 is a flowchart showing an exemplary method 900 for manufacturingan electrical implantable lead 14 according to another embodiment of thepresent disclosure. The method begins with extruding a polymericmaterial through a die including pins (further described with respect toFIG. 10) to form lumens (step 910). In various embodiments, the die andpins are designed to create a plurality of lumens within the implantableelectrical lead. These lumens extend along a longitudinal axis of thedie. Next, the die and pins are twisted (i.e., rotated) with respect tothe longitudinal axis alternatively in a clockwise and acounterclockwise direction while extruding (step 920), such thattwisting in the clockwise direction creates a trough and twisting in thecounterclockwise direction creates a crest in the plurality of thelumens. Then, a conductor cable may be inserted into each of theplurality of the lumens (step 930). FIG. 10 is a schematic view furtherillustrating the method 900. As shown in FIG. 10, the method 900 resultsin a lead (or lead segment) having an oscillating lumen 76 formed alonga longitudinal axis of the lead. As shown at 1010, extrusion of the leadbegins with the die and pins in a first position. Then, as extrusion ofthe lead body continues, the die and pins are rotated in a clockwisedirection to clockwise position 1020, a trough 60 is formed in the lumen76. Next, as extrusion continues, the die and pins are rotatedcounterclockwise through the original position 1010 and further tocounterclockwise position 1030, which forms a crest 56 in the lumen 76.Finally, the dies and pins are rotated clockwise back to the originalposition 1010. This process may then be repeated as desired to createfurther oscillations in the lumen 76. The relative speed of extrusion(i.e., longitudinal extension of the lead body) and rotation of the dieand pins determine the angular frequency of the lumen 76, and the degreeof rotation of the die and pins determine the amplitude of the lumen 76.

FIG. 11 is a perspective view of a lead 14 according to other disclosedembodiments. As shown in FIG. 11, the lead 14 (or lead segment) includesa plurality of lumens 52, 54 having an oval- or elliptical-shapedcross-section. According to various embodiments, this structure isformed by extruding a lead body segment having lumens with oval- orelliptical-shaped cross-sections. As shown, this oval- orelliptical-shaped cross-section allows the conductors (e.g., cables) 64,66 located within the lumens 52, 54 to have a non-linear (e.g.,oscillating or sinusoidal) configuration.

As shown in FIG. 12, in these embodiments, the lumens 52, 54 follow agenerally straight or linear path along the longitudinal axis of thelead 14. As shown in FIG. 12, the conductor cables 64, 66, disposedwithin the plurality of lumens 52, 54, having an inherent undulating ornon-linear shape. In various embodiments, the non-linear shape of theconductors or cables 64, 66 includes a plurality of crests 56, 58 andtroughs 60, 62. These crests and troughs in the cables may be similar tothe sinusoidal oscillations illustrated and explained in conjunctionwith previous embodiments related to the crests and the troughs of thenon-linear lumens of FIGS. 2-10. In accordance with the embodimentsshown in FIGS. 11 and 12, the undulating or non-linear pattern of theconductor cables provides a slack to the conductor cables, whichprovides relief during bending of the lead. In accordance with theseembodiments, and as illustrated in FIGS. 11 and 12, the diameter of thelumens 52, 54 are equal to or greater than the amplitude of theconductors or cables 64, 66.

The undulating or non-linear conductors 64, 66 described in conjunctionwith FIGS. 11 and 12 may be formed according to any of a variety ofmethods. According to exemplary embodiments, the method includes coatinga cable with a thermoplastic such as for example ethylenetetrafluoroethylene (ETFE) or polytetrafluoroethylene (PTFE). The coatedcables are then inserted into a die having a defined shape (e.g.,oscillating or sinusoidal). The method further includes heating thecoated cables to set the shape of the thermoplastic material. In someembodiments, the die can have a sinusoidal shape. The amplitude andfrequency of the sinusoidal shape may be selected to optimize flexperformance and stringability of the cables in the lead body lumens. Inother embodiments, the cables coated with a thermoplastic are forcedinto a helix, spiral, or coil shape by wrapping the coated cables arounda mandrel. The mandrel is then heated sufficiently to heat-set thethermoplastic coating such that cables retain the spiral shape after themandrel is removed. In other embodiments, the undulations in the cableare formed by placing the cable into a die defining the desired shape,then overmolding the cables with a polymer (e.g., silicone rubber) tomaintain the desired shape. According to other embodiments, theundulating or non-linear shape is imparted to the conductors by bendingthe conductors past their yield point such that the conductors retainthe desired shape. This bending may be accomplished, for example bybending the cable around a small diameter pin. In other embodiments, themethod of manufacturing may involve stringing a straight cable into alarger diameter lumen and then pushing a part of the cable extendingoutside the lead body into the lumen, which will cause the cable tobuckle and undulate inside the lumen.

FIG. 13 shows another embodiment for forming undulations in a cable. Asshown, a cable 64 is inserted into a polymer tube 78 having a preformedoscillating or undulating shape. According to some embodiments, thepolymer tube 78 is formed by molding a polymer (e.g., silicone rubber orpolyurethane) over an undulating mandrel or core. As the cable 64 isinserted into the undulating polymer tube 78, it takes on the undulatingshape of the polymer tube 78. In another exemplary embodiment, a moldedlead or terminal boot with undulating cables can be manufactured byinjecting silicone rubber (or polyurethane or similar elastomericpolymer with low durometer between Shore 60D and 40A) over core pinsthat have a sinusoidal shape. The core pins are then removed to createlumens. When silicone rubber is used for molding, the molded part can beswelled in heptane or hexane. For other polymers that are not easilyswelled, if the core pins are easily malleable, they may be put intension until they are approximately straight and capable of beingpulled out. In some embodiments, the core pins are provided with a lowfriction coating (e.g., PTFE) to facilitate removal. In otherembodiments, the core pins are made out of a shape memory alloy havingan undulating austentitic shape and a straight martensitic shape. Inthese embodiments, the core pin can be used in an overmolding process,then placed in a cold temperature environment (e.g., dipped in coldwater) to straighten the core pin to facilitate removal.

After the conductors or cable are formed into a non-linear (e.g.,oscillating, undulating, etc.) shape using a technique described herein,the conductors are inserted into the oval or elliptical lumens.According to embodiments where the cable or conductor is formed as aspiral or helix, the corresponding lumen in the lead body may also havea circular shape having a sufficiently large diameter to accept thecable or conductor in its spiral or helical shape. The resultingstructure provides for a cable or conductor having an overall lengthgreater than a length of the lumen, which helps minimize stress (andthus fatigue) during bending of the lead.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentinvention. For example, while the embodiments described above refer toparticular features, the scope of this invention also includesembodiments having different combinations of features and embodimentsthat do not include all of the above described features.

We claim:
 1. An implantable medical lead, comprising: an elongated leadbody extending longitudinally and having a plurality of lumens therein,including at least one linear lumen and a first non-linear lumenextending longitudinally along a portion of the lead body, the at leastone linear lumen and the first non-linear lumen adjacent in the portionof the lead body, the first non-linear lumen on a non-helical andnon-linear path relative to the portion of the lead body such that thefirst non-linear lumen extends longitudinally in a rotational plane, thefirst non-linear lumen including a plurality of crests and a pluralityof troughs in the rotational plane such that some portions of thenon-linear lumen extend longitudinally clockwise and other portionsextend longitudinally counterclockwise; a plurality of conductor cablesdisposed within the plurality of lumens; a terminal connector coupled toa proximal end of the lead body, the terminal connector in electricalcommunication with at least one of the plurality of conductor cables;and at least one electrode coupled to the lead body, the at least oneelectrode in electrical communication with at least one of the pluralityof conductor cables; wherein the first non-linear lumen is configured toprovide strain relief to at least one of the plurality of conductorcables.
 2. The implantable medical lead of claim 1, further comprising asecond non-linear lumen extending longitudinally along a portion of thelead body.
 3. The implantable medical lead of claim 2, wherein the firstand second non-linear lumens are offset from a central axis of theelongated lead body.
 4. The implantable medical lead of claim 2, whereinthe first non-linear lumen and the second non-linear lumen have equalfrequencies and amplitudes.
 5. The implantable medical lead of claim 2,wherein the first non-linear lumen has a first frequency and the secondnon-linear lumen has a second frequency that is not equal to the firstfrequency.
 6. The implantable medical lead of claim 1, wherein theplurality of lumens have a circular cross-section.
 7. The implantablemedical lead of claim 1, wherein the series of crests and troughs definea sinusoidal pattern with a defined amplitude and a defined angularfrequency.
 8. The implantable medical lead of claim 1, wherein the firstnon-linear lumen extends along the portion of the lead body extendingabout 10 about 50 mm from the terminal connector.
 9. An implantablemedical lead, comprising: an elongated lead body extendinglongitudinally and having a plurality of lumens therein, including atleast one linear lumen and a first non-linear lumen extendinglongitudinally along a portion of the lead body, the at least one linearlumen and the first non-linear lumen adjacent in the portion of the leadbody, the first non-linear lumen extending longitudinally in arotational plane, the first non-linear lumen including a plurality ofcrests and a plurality of troughs in the rotational plane such that thefirst non-linear lumen has oscillations along the portion; a pluralityof conductor cables disposed within the plurality of lumens; a terminalconnector coupled to a proximal end of the lead body, the terminalconnector in electrical communication with at least one of the pluralityof conductor cables; and at least one electrode coupled to the leadbody, the at least one electrode in electrical communication with atleast one of the plurality of conductor cables.
 10. The implantablemedical lead of claim 9, further comprising a second non-linear lumenextending longitudinally along a portion of the lead body.
 11. Theimplantable medical lead of claim 10, wherein the first and secondnon-linear lumens are offset from a central axis of the elongated leadbody.
 12. The implantable medical lead of claim 10, wherein the firstnon-linear lumen and the second non-linear lumen have equal frequenciesand amplitudes.
 13. The implantable medical lead of claim 10, whereinthe first non-linear lumen has a first frequency and the secondnon-linear lumen has a second frequency that is not equal to the firstfrequency.
 14. The implantable medical lead of claim 9, wherein theplurality of lumens have a circular cross-section.
 15. The implantablemedical lead of claim 9, wherein the series of crests and troughs definea sinusoidal pattern with a defined amplitude and a defined angularfrequency.
 16. The implantable medical lead of claim 9, wherein thefirst non-linear lumen extends along the portion of the lead bodyextending about 10 about 50 mm from the terminal connector.
 17. Animplantable medical lead, comprising: an elongated lead body extendinglongitudinally and having a plurality of lumens therein, including atleast one linear lumen and a first non-linear lumen extendinglongitudinally along a portion of the lead body, the at least one linearlumen and the first non-linear lumen adjacent in the portion of the leadbody, the first non-linear lumen extending longitudinally in arotational plane, the first non-linear lumen including a plurality ofcrests and a plurality of troughs in the rotational plane such that thefirst non-linear lumen has a waveform shape in the rotational planealong the portion; and a plurality of conductor cables disposed withinthe plurality of lumens, wherein the first non-linear lumen isconfigured to provide strain relief to at least one of the plurality ofconductor cables.
 18. The implantable medical lead of claim 17, furthercomprising a second non-linear lumen extending longitudinally along aportion of the lead body.
 19. The implantable medical lead of claim 17,wherein the first non-linear lumen is offset from a central axis of theelongated lead body.
 20. The implantable medical lead of claim 17,wherein the rotational plane is defined about a longitudinal center axisof the lead.